<< >> NASA ASRS Report 522210, August 2001

Approaching traffic on TCASII causes a crew to question ATC who notes that they have descended through their cleared altitude.

Attributes
ACN	522210
Time
Date	200108
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dtw.airport
State Reference	MI
Altitude	msl bound lower : 4600 msl bound upper : 5000
Environment
Flight Conditions	Mixed
Light	Night
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	DC-9 50
Flight Phase	descent : approach
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 65 flight time total : 12000 flight time type : 8000
ASRS Report	522210
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : published procedure non adherence : clearance
Resolutory Action	controller : issued advisory controller : issued new clearance flight crew : returned to assigned altitude
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We thought ATC gave us clearance from 6000 ft to 4000 ft and acknowledged. Both of us repeated 4000 ft as set in altitude warning indicator. (I was PNF and think I answered ATC 6000 ft for 4000 ft, but when you're filling out a NASA form you're no longer 100% sure). I saw traffic coming on TCASII and queried ATC. They said we were supposed to be at 5000 ft and to climb back to it, we were at 4600 ft and climbed back up. If we were given 5000 ft and I acknowledged 6000 ft for 5000 ft and put 4000 ft in the altitude warning indicator, I am definitely the one at fault and thankful for TCASII onboard.

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Original NASA ASRS Text

Title: APCHING TFC ON TCASII CAUSES A CREW TO QUESTION ATC WHO NOTES THAT THEY HAVE DSNDED THROUGH THEIR CLRED ALT.

Narrative: WE THOUGHT ATC GAVE US CLRNC FROM 6000 FT TO 4000 FT AND ACKNOWLEDGED. BOTH OF US REPEATED 4000 FT AS SET IN ALT WARNING INDICATOR. (I WAS PNF AND THINK I ANSWERED ATC 6000 FT FOR 4000 FT, BUT WHEN YOU'RE FILLING OUT A NASA FORM YOU'RE NO LONGER 100% SURE). I SAW TFC COMING ON TCASII AND QUERIED ATC. THEY SAID WE WERE SUPPOSED TO BE AT 5000 FT AND TO CLB BACK TO IT, WE WERE AT 4600 FT AND CLBED BACK UP. IF WE WERE GIVEN 5000 FT AND I ACKNOWLEDGED 6000 FT FOR 5000 FT AND PUT 4000 FT IN THE ALT WARNING INDICATOR, I AM DEFINITELY THE ONE AT FAULT AND THANKFUL FOR TCASII ONBOARD.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.